Properties of Nanocrystals-formulated Aluminosilicate Bricks

In the present work, seven different types of nanocrystals were studied as additives in the formulation of aluminosilicate bricks. The considered nanocrystals consisted of anatase titanium dioxide (two differently shaped types), boron modified anatase, calcium carbonate (in calcite phase), aluminium hydroxide and silicon carbide (of two diverse sizes), which were prepared using different methods. Syntheses aim to give a good control over a particle’s size and shape. Anatase titania nanocrystals, together with the nano-aluminium hydroxide ones, were synthesized via microwave-assisted procedures, with the use of different additives and without the final calcination steps. The silicon carbide nanoparticles were prepared via laser pyrolysis. The nano-calcium carbonate was prepared via a spray drying technique. All of the nanocrystals were tested as fillers (in 0.5, 1 and 2 wt. % amounts) in a commercial aluminosilicate refractory (55 % Al2O3, 42 % SiO2). They were used to prepare bricks that were thermally treated at 1300 °C for 24 hours, according to the international norms. The differently synthesized nanocrystals were added for the preparation of the bricks, with the aim to improve their heat-insulating and/or mechanical properties. The nanocrystals-modified refractories showed variations in properties, with respect to the untreated aluminosilicate reference in heat-insulating performances (thermal diffusivities were measured by the “hot disk” technique). In general, they also showed improvements in mechanical compression resistance for all of the samples at 2 wt. %. The best heat insulation was obtained with the addition of nano-aluminium hydroxide at 2 wt. %, while the highest mechanical compression breaking resistance was found with nano-CaCO3 at 2 wt. %. These outcomes were investigated with complementary techniques, like mercury porosimetry for porosity, and Archimedes methods to measure physical properties like the bulk and apparent densities, apparent porosities and water absorption. The results show that the nano-aluminium hydroxide modified bricks were the most porous, which could explain the best heat-insulating performances. There is a less straightforward explanation for the mechanical resistance results, as they may have relations with the characteristics of the pores. Furthermore, the nanoparticles may have possible reactions with the matrix during the heat treatments

Thermal and mechanical performance of rigid polyurethane foam added with commercial nanoparticles

This study investigates the effects of commercial nanoparticles on thermal and mechanical performance of rigid polyurethane foams. Two different types of nanoparticles are considered as fillers, spherical titania and rod-shaped halloysite clay nanotubes. The aim of this study was to produce rigid polyurethane foams modified with titania nanocrystals and nanohalloysite in order to obtain polyurethanes with improved properties. The laboratory scale-up will be suitable for the production in many branches of industry, such as construction and automotive production. In particular, these foams, added with commercial nanoparticles, characterized by better thermal and mechanical properties, are mainly used in construction for thermal insulation of buildings. The fillers were dispersed in the components, bringing rates up to 10%. In these investigations, the improvement of the thermal properties occurs by adding nanoparticles in the range 4–8% of titania and halloysite. The mechanical properties instead have been observed an improvement starting from 6% of nanoparticles addition. All data are in agreement with scanning electron microscope observations that shown a decrease in the average cell size and an increase in the cell density by adding nanoparticles in foams

Facile preparation of TiO2-polyvinyl alcohol hybrid nanoparticles with improved visible light photocatalytic activity

Hybrid inorganic/organic core/shell nanoparticles were prepared through a two step synthesis procedure. In the first step, pure anatase TiO2 nanoparticles were synthesized though a rapid microwave assisted non-aqueous route. Then, the obtained titania nanoparticles were coated with polyvinyl alcohol (PVA) using a simple solution method followed by relatively low temperature treatment. The PVA-coated titania nanoparticles samples were prepared at different TiO2–PVA weight ratio and they were characterized using X-Ray diffraction, transmission electron microscopy, infrared spectroscopy and Brunauer–Emmett–Teller (BET) analysis. Photocatalytic performance was also evaluated for all samples and the results indicated that TiO2:PVA weight ratio was a key factor to obtain an improvement of the photocatalytic activity with respect to bare TiO2 nanoparticles, since PVA concentration influenced the surface area and the aggregation of nanoparticles and the thickness of the coating layer. This inexpensive system provides a simple, quick and effective approach which allows to obtain core/shell hybrid nanostructures

Enhanced photocatalytic activity of pure anatase Tio<inf>2</inf> and Pt-Tio<inf>2</inf> nanoparticles synthesized by green microwave assisted route

High-yield, rapid and facile synthesis of elongated pure anatase titania nanoparticles has been achieved through a nonaqueous microwave-based approach. The residual organics onto nanoparticles surfaces were completely removed through a new treatment under ozone flow, at room temperature in air. Such an ozone cleaning method revealed an effective inexpensive dry process of removing organic contaminants from nanoparticles surfaces. The TiO2 elongated nanoparticles having a length of 13.8 +/- 5.5 nm and a diameter of 9.0 +/- 1.2 nm were characterized by powder X-Ray diffraction, transmission electron microscopy, selected area diffraction, BET surface area analyzer and FT-IR spectroscopy. Photocatalytic evaluation demonstrated that the as-synthesized ozone-cleaned TiO2 nanoparticles and TiO2 nanoparticles loaded with platinum possess excellent Rhodamine B performance with respect to both commercial spherical nanotitania P25 and P25 loaded with platinum. This could be attributed to the anatase phase purity, small size, large specific surface area and clean surfaces of the prepared nanoparticles

Selective synthesis of TiO2 nanocrystals with morphology control with the microwave-solvothermal method

In this paper, a method to synthesize anatase TiO2 nanorods by hydrolysis of titanium (IV) isopropoxide (TTIP) in the presence of benzyl alcohol and acetic acid, at 210 oC was tested. The novelty of the present approach relies on the test of shape-controlled synthesis of anatase TiO2 nanocrystals, via microwave-solvothermal method in 45 min. The different TiO2 nanocrystals were obtained tuning the TTIP-acetic acid ratio under optimized synthetic conditions and were characterized in detail by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), Micro Raman (together with microphotoluminescence) and FT-IR spectroscopies. Acetic acid coordinated on the nanocrystal surface was removed by the reduction of its carboxyl group via a “super-hydride reaction”, and the photocatalytic activity of bare TiO2 nanocrystals, under visible light irradiation, was also evaluated: the best performing TiO2 anatase nanocrystals exhibited a discrete photoactivity, completely degrading a Rhodamine B solution in five hours

Interaction between Human Serum Albumin and Different Anatase TiO2 Nanoparticles: A Nano-bio Interface Study

In this investigation, differently shaped and surface functionalized TiO2 anatase nanoparticles and human serum albumin (HSA) were selected to study proteinnanoparticles interaction both in a solution and on flat surfaces, thereby mimicking a medical device. Anatase nanocrystals were characterized by transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) surface analysis and dynamic light scattering (DLS). The proteinnanoparticles’ interactions and their eventual reversibility were studied by pH dependent ζ- potential measurements in different media: ultra-pure water, a phosphate buffer simulating physiological conditions and in a culture medium supplemented with foetal bovine serum. The protein corona masking effect was evidenced and the interaction HSA-nanocrystals resulted irreversible. The interaction HSA-silicon supported TiO2 nanocrystals films was studied by atomic force microscopy (AFM), and resulted driven by the substrate hydrophilicity degree plus was different for the diverse range of nanocrystals tested. Surface roughness measurements showed that on some of the nanocrystals, HSA were arranged in a more globular manner. A lower protein affinity was found for nanocrystals that had a smaller primary particle size, which may correspond to their higher biocompatibility. This nano-bio interface research aimed to study the HSA protein-TiO2 anatase nanocrystals under conditions similar to those for in vitro and in vivo toxicity analyses

Efficient, Green Non-aqueous Microwave-assisted Synthesis of Anatase TiO2 and Pt Loaded TiO2 Nanorods with High Photocatalytic Performance

A high-yield synthesis of pure anatase titania nanorods has been achieved through a nonaqueous microwave-based approach. The residual organics on nanoparticles surfaces were completely removed under ozone flow at room temperature in air. The TiO2 nanorods, with average lengths of 27.6 ± 5.8 nm and average diameters of 3.2 ± 0.4 nm, were characterized by powder X-Ray diffraction, transmission electron microscopy, selected area diffraction, BET surface area analysis and FT-IR spectroscopy. The photocatalytic performances of the as-synthesized TiO2 nanorods and platinum loaded TiO2 nanorods were implemented with respect to both commercial P25 and platinum loaded P25. Performance enhancements should be attributed to effects like differences in the adsorption capacity and in the separation efficiency of the photogen‐ erated electrons-holes

Properties of aluminosilicate refractories with synthesized boron-modified TiO2 nanocrystals

An efficient microwave supported synthesis, with a reaction time of only one and a half minute, to prepare boron-modified titania nanocrystals TiO2:(B), was developed. The nanocrystals were obtained by hydrolysis of titanium tetraisopropoxide (TTIP) together with benzyl alcohol and boric acid, and the approach did not need surfactants use and a final calcination step. The produced TiO2:(B) nanocrystals were characterized in detail by low magnification Transmission Electron Microscopy (TEM), Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES), X-Ray Diffractometry (XRD), and a Micro Raman Spectroscopy. One of the obtained samples was then tested as an additive in various amounts in a typical aluminosilicate refractory composition. The effects of these additions in bricks were evaluated, according to UNI EN 196/2005, in terms of thermo-physical and mechanical properties: diffusivity, bulk density, apparent density, open and apparent porosity and cold crushing strength. Bricks’ microstructure was analysed by Scanning Electron Microscopy (SEM) and energy dispersion spectroscopy (EDS). The bricks obtained with nanoadditives presented improved mechanical characteristics with respect to the typical aluminosilicates, presumably because of a better compaction during the raw materials’ mixing stage